Currently I am working on high-speed (DC-DC supplied) insulated multilevel gate drivers. (without optos!) Such gate drivers allow for the construction of fast [ns] Solid State Relays (that's what these two MOSFETs in series oppositions are) which make it possible to work around the evil* Miller effect and allow MOSFETs to be used in place of diodes (for synchronous rectification) and bidirectional switching as well as for high-side switching with N-Ch MOSFETs (which have a lower R DS(ON) and are cheaper than P-Ch) Besides obvious applications in this CARA experiment, such galvanically isolated gate drivers are also useful in all kinds of motor driving schemes, full H-bridges, solar regulators , battery chargers, DC-->AC inverters, PWM servos, etc... They also completely avoid the inconvenient ground loops between scopes and signal generators.  * The Miller effect occurs in all inverting switches/amplifiers (such as transistors working in common emitter or common source modes) where a capacitance exists between the output and the input. This effect is responsible for slowing down of transistor's switching speeds and sometimes is responsible for parasitic Miller oscillations that waste a lot of energy. In MOSFETs, it occurs anytime the voltage between the drain and the gate changes rapidly (high dv/dt). However when an isolated gate driver is used, then it is possible to operate the MOSFET in a non-inverting common drain configuration (a.k.a. the source follower) and avoid the high dv/dt between its drain and gate, altogether. Because of this, the transistor switches faster and cannot suffer from Miller oscillations and ground loops. The burden of the high switching dv/dt is transferred from the transistor to the isolation barrier of the driver.
« Last Edit: 2015-03-09, 01:21:11 by verpies »
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Topic: Magnetic CARA - Proof of Concept (Read 69682 times)
